Its "amateur" radio, not to be stolen and taken over by encrypted taxi dispatchers or pay per view encrypted TV broadcasters. The FCC likes to separate human activities by frequency band, and gets all out of whack when people try to sneak around their intentions. In no small part because of licensing procedures and fees which are darn near zilch for ham radio and quite expensive process for some LMR and broadcasting operations.

Its also kind of vital for international communication into repressive regimes (worse than the USA in 2010s anyway). Think of a kid in Wisconsin talking to a dude in Russia during the peak of the cold war, that kind of thing. Now "everybody knows" that you can trivially embed a one time pad, but at least we're not sending character groups containing who knows what to each other. So pretty much everywhere except utterly failed states, you can get an amateur radio license and just kind of hang out on the air. Its the original techie social network, from decades before the internet.

Finally at least in theory its supposed to be one big party line for general purposes and emergency communications. So partitioning the service into little encrypted groups who intentionally would not be able to talk with each other, serves exactly what purpose given the intentional regulatory design to encourage the exact opposite goal? It would be like allowing encrypted messages on Hacker News comments, which would serve exactly what purpose, if any?